Maillard Reaction
Maillard Reaction: Myths and Caramelization in Coffee
The Maillard reaction and coffee caramelization are two chemical phenomena that act differently in building the sensory profile of the roasted bean.
The Maillard reaction occurs mainly between 140 °C and 165 °C and involves the interaction between amino acids and reducing sugars. This process is responsible for the formation of complex flavors and aromas. Caramelization, on the other hand, only occurs above 170 °C, involves exclusively sugars, and does not depend on the presence of proteins.
Definition of the Maillard Reaction
During the Maillard reaction, amino acids react with reducing sugars present in green beans, giving rise to melanoidins, brown-colored compounds that directly influence the flavor, aroma, and body of the beverage. Among the sugars involved, glucose and fructose play a predominant role.
In medium roasts, this phase usually lasts between 4 and 8 minutes. During this interval, the bean changes from green to light brown, while volatile compounds begin to form, creating characteristic toasted aromas. Pyrazines, for example, appear in the early stages and impart nutty notes, while chocolate nuances appear in later stages of development.
Adequate ventilation favors these reactions by providing fresh oxygen to the system. However, excess ventilation can cause unwanted oxidation. Similarly, residual moisture around 5% tends to delay the start of the reaction, making pre-drying the bean an important factor for the efficiency of the process.
Exact moment of the start
Roasting begins with the dehydration phase, around 100 °C, when the water present in the bean begins to evaporate. As the temperature approaches 140 °C, the Maillard reaction is activated.
The so-called first crack occurs between 195 °C and 205 °C. From this point on, the roasting process usually occupies 20% to 25% of the total time, being crucial for the sensory balance of the beverage.
Arabica coffees tend to respond more quickly to the Maillard reaction due to their higher protein content, while wetter beans require slower heating ramps to avoid defects. Therefore, roasting masters closely monitor the ROR (Rate of Rise) curves, ensuring greater precision in thermal control.
Myths of Caramelization
One of the most common misconceptions is attributing all the brown coloration of coffee to caramelization. In reality, in light and medium roasts, the Maillard reaction is predominant, while caramelization only occurs at higher temperatures.
Another recurring myth is the idea that the Maillard reaction degrades caffeine. Studies show that caffeine remains stable up to approximately 230 °C. Excessive bitterness, in turn, is more associated with darker roasts and excessive exposure time to heat.
Furthermore, accelerated roasting can result in underdevelopment of the Maillard reaction, generating vegetal flavors and little sensory complexity.
Chemical Phases
In the initial stages, Amadori products are formed, which evolve into more complex compounds, such as melanoidins. Molecules like 2-furfurylthiol are responsible for the classic coffee aroma, while the body of the beverage is also strongly linked to these compounds.
The naturally more acidic pH of many Brazilian beans favors these reactions, although there are variations between regions and cultivars. Slower roasts tend to maximize complexity, while very fast processes limit the number of compounds formed.
In terms of color, the Agtron 60-70 range usually indicates a suitable point after the Maillard phase, especially for coffees with a balanced profile.
Process Control and Roast Levels
Precise control of temperature, airflow, and time is essential for a uniform Maillard reaction during roasting, avoiding localized burns due to thermal peaks. Homogeneous grains in size and density help in the regular distribution of heat, promoting consistency.
In light to medium-light roasts, the Maillard reaction balances acidity and initial sweetness. Medium roasts intensify sweet notes through greater development of aromatic compounds. Dark roasts prioritize advanced carbonation and caramelization, reducing the relative impact of the Maillard reaction in favor of toasted and intense flavors.
In Brazil, medium roasts are popular in traditional consumption, aligned with ABIC standards that emphasize quality and standardization in roasted coffees. Foreign markets value consistency and similar standards for export.
SIATEC Brazil® Technology
SIATEC roasters apply precisely this control of temperature, airflow, and time for uniform Maillard reactions at all roast levels. Its negative pressure chamber, generated by two independent furnaces (one for hot air and the other for burning smoke and gases), promotes roasting from the inside out. Thus, it standardizes the roasting point and optimizes the Maillard reaction, preventing localized burns even in batches with varied beans.
The system reduces contact with smoke, enhances sensory quality, and minimizes acrylamide via dedicated software. Fluidized bed, air control, and paddles ensure thermal homogeneity, stability, and repeatability, ideal for medium Brazilian roasts or export. With fast cycles, a minimum yield of 3% per bag, and high capacity, they surpass conventional systems in productivity.
Discover how SIATEC Brazil® technology optimizes your roasting and raises the standard of your coffee.